I'm pretty new to javascript, so apologies for the beginner question. Basically, I am having some problems with the window.open() method.
My code essentially takes a user string, adds a couple different variations to it, and those searches those different variations, and then is supposed to open a new window with each result. However, it seems that after my first window.open statement, the code stops executing. This is what I am working with:
var searchStrings = new Array(url1, url2, url3);
var arrayLength = searchStrings.length;
for (var i = 0; i<arrayLength; i++) {
window.open(searchStrings[i]);
}
I have tested the loop with code other than window.open to make sure it iterates through the array correctly, and I have set i to values higher than 0 to test opening the second or third item in the array.
It seems like window.open is only meant to be used once, or am I doing something else incorrectly?
Check this out: https://javascript.info/popup-windows
This documents correct usage of window.open() functionality.
Modern browsers block that kind of execution, due the risk of mis-using the functionality.
Imagine, you enter the page and 10x windows open, for no reason.
Actually, have a look you code works but chrome blocks the window and on the address bar you are notified. However Firefox blocks it completely, until manually disable the option.
windows.open can takes second parameter(name), if you want open multiple URLs you have to set unique name for each one. in your scenario you cant use this:
for (var i = 0; i < arrayLength; i++) {
window.open(searchStrings[i], '_wnd' + i);
}
Related
Like the title said, how do I get all elements from a scroll div? The elements in the scroll list are loaded and destroyed dynamically.
I tried to crawl all course names from this website:
https://public.enroll.wisc.edu/search?term=1204
The code below only works for one time:
let list = document.getElementsByClassName('md-virtual-repeat-scroller')[0]
let childs = document.getElementsByClassName("result__name")
console.log(childs[0].innerText)
However, if I do this, I will get the same result for 10 times:
let list = document.getElementsByClassName('md-virtual-repeat-scroller')[0]
for(let i = 0; i < 10; i++) {
let childs = document.getElementsByClassName("result__name")
for(let j = 0; j < childs.length; j++) {
console.log(childs[j].innerText)
}
// scroll by 1000px every time
list.scrollBy(0, 1000)
}
I don't know what's the problem. Is it because that scrollBy() works asynchronously? But I tried to use async and await. It still doesn't work.
Give more information in less words as a possible. Many problems could be related to browser and its version, for example. How is this script called? Are you giving commands via browser console? Have you done a copy of the site and performed some modification on it? It's hard to understand the problem in a realistic level.
Tip: Avoiding use innerText. It's slower and is supported in many browsers only for compability to scripts written to old versions of IE. (I don't know why so many examples in internet use it as first option). User textContent instead.
It's always good to test the returned value of a function/methods - specially during the development of the program.
Never ask to the StackOverFlow community (and to any other) to write progams for you!
You question "how do I get all elements from a scroll div?" is so "loose". scroll div? The answer to this, independently to the "type of div" (and tag!) would be found below.
Your code seems to be no sense in order to do what you want. Why iterate from 0 to 10?
Look at this snipet. I think it will help you
const list = document.getElementsByClassName('md-virtual-repeat-scroller')[0];// if there is no intention to reassign it. Use [0] if you are sure it's the first element of this collection
let childs = list.getElementsByClassName("result__name"); // get only elements inside the first variable!
Use the iterator of the variable.
for(item of childs)
{
/*code*/
}
I am sure you will achieve your goals!
And never suggest us (Community) to code for you or even to resolve your problem. This sound very agressive! To you too! I'm sure.
I solved my problem by reading this article:https://intoli.com/blog/scrape-infinite-scroll/
The reason why I kept getting the same elements is that scrollBy() works asynchronously, so I have to wait then evaluate the page again. I am using puppeteer by the way.
please read the article, super helpful.
This may be a quite naive question but I really need some help.
Prior to writing this post, I was programming on JSBin. Turns out without me realizing, I ran a setInterval loop prompting for userInput and it kept on looping, making me unable to click anywhere to change the code to fix the loop. It kept on repeating and repeating. It got to the point where I had to refresh and lose all my hard-written-code (I was not logged in, so my code was not saved)! I want to avoid that next time.
So, my question is how do I stop any such kind of setInterval Loops, so that I am able to access my code and change it and re-run it. Below is a code that demonstrates my issue, if you try running it on JSBin.com (obviously, it is not the code I wrote before). As you can see, I can not click on my code to change it (or save it) in any way, which means I lose all my code!
This may seem like a useless question, but I really want to know ways to fix it and perhaps fixing it from the developer tools will help me be familiar with the overwhelming set of tools it has :P. So please help me if you know a solution.
Thank you for taking your time to help me! I appreciate it.
setInterval(demo,1);
function demo()
{
var name = prompt("Enter your name: ");
}
Another option is to search the developer tools "Elements" panel for the iframe (this should be doable even if the main document is unresponsive due to prompt's blocking) - then, just right click the iframe element and remove it, no need to type any Javascript. (or, if you want you can select the iframe with querySelector and remove it, eg document.querySelector('iframe').remove())
That's kind of a hack and should only be used in cases like the one exposed in OP but,
About all implementations use integers as timerid that just get incremented at every call.
So what you can do, is to clear all timeouts that were created on the page.
To do so you need to first get to which timerid we are, then call cleatTimeout or clearInterval (they do the same) in a loop until you reach the last call:
function stopAllTimers() {
const timerid = setTimeout(_=>{}); // first grab the current id
let i=0;
while(i < timerid) {
clearTimeout(i); // clear all
i++;
}
};
btn.onclick = stopAllTimers;
// some stoopid orphan intervals
setInterval(()=>console.log('5000'), 5000);
setInterval(()=>console.log('1000'), 1000);
setInterval(()=>console.log('3000'), 3000);
const recursive = () => {
console.log('recursive timeout');
setTimeout(recursive, 5000);
};
recursive();
<button id="btn">stop all timeouts</button>
Assuming the dev tools are closed, hit esc and f12 nearly simultaneously. This should open the dev tools. If it doesn't keep trying until it does.
Once they are open, hit esc and f8. Again, retry til it halts javascript execution at some arbitrary point in the code.
In the "sources" tab locate the generated script for what you wrote (offhand I don't know how it would look like from within JSBin) and literally delete the var name = prompt("Enter your name: "); line. Hitting f8 again will continue execution as if the "new" code is running. This should free you up to copy/paste your code from the site itself before you refresh the page
I am writing a greasemonkey script. Recently i had this same problem twice and i have no idea why is this happening.
function colli(){
.....
var oPriorityMass = bynID('massadderPriority');//my own document.getElementById() function
var aPriorities = [];
if (oPriorityMass) {
for (var cEntry=0; cEntry < oPriorityMass.childNodes.length; cEntry++) {
var sCollNumber = oPriorityMass.childNodes[cEntry].getAttribute('coll');
if (bynID('adder' + sCollNumber + '_check').checked)
aPriorities.push(parseInt(sCollNumber));
}
}
.....
}
So the mystery of this is, one day i had oPriorityMass named as oPririoty. It was working fine, but the whole function was not yet complete and i started working on another functions for my script. These functions have no connection with each other.
Few days later i decided to go back to my function in the above example and finish it. I ran a test on it without modifying anything and got an error in the firefox's (4) javascript error console saying that oPriority.chilNodes[cEntry] is undefined. NOTE, few days back i have tested it exactly the same way and there was no such problem at all.
Ok, so, i decided to rename oPriority to oPriorityMass. Magically, problem got solved.
At first i thought, maybe there was some conflict of 2 objects, with the same name being used in different functions, which somehow continued to live even outside of function scope. My script is currently over 6000 lines big, but i did a search and found out that oPriority was not mentioned anywhere else but in this exact function.
Can somebody tell me, how and why is this happening? I mentioned same thing happened twice now and they happened in different functions, but the same problem node.childNodes[c] is undefined yet node is not null and node.childNodes.length show correct child count.
What is going on? How do i avoid such problems?
Thank you
EDIT: The error given by error console is
Error: uncaught exception: TypeError: oPriorityMass.childNodes[cEntry] is undefined
In response to Brocks comment:
GM_log(oPriorityMass.childNodes[cEntry]) returns undefined as a message. So node.childNodes[c] is the thing that is undefined in general.
My script creates a div window. Later, the above function uses elements in this div. Elements do have unique IDs and i am 100% sure the original site don't know about them.
My script has a start/stop button to run one or the other function when i need to.
I have been refreshing the page and running my script function now. I have noticed that sometimes (but not always) script will fail with the described error on the first run, however, if i run it again (without refreshing the page) it starts working.
The page has a javascript that modifies it. It changes some of it's element widths so it changes when the browser is resized. But i know it has no effect on my div as it is left unchanged when i resize browser.
EDIT2:
function bynID(sID) {
return top.document.getElementById(ns(sID));
}
function ns(sText) {
return g_sScriptName + '_' + sText;
}
ns function just adds the script name in front of the ID. I use it when creating HTML element so my elements never have the same id as the web page. So bynID() is simple function that saves some typing time when i need to get element by ID.
I have modified my colli() function to include check
if (oPriorityMass) {
if (!oPriorityMass.childNodes[0]) {
GM_log('Retrying');
setTimeout(loadPage,2000);
return;
}
for (var cEntry=0; cEntry < oPriorityMass.childNodes.length; cEntry++) {
var sCollNumber = oPriorityMass.childNodes[cEntry].getAttribute('coll');
if (bynID('adder' + sCollNumber + '_check').checked)
aPriorities.push(parseInt(sCollNumber));
}
}
The loadPage function does 1 AJAX call, then i run few XPATH queries on it, but the actual contents are never appended/shown on the page, just kept inside document.createElement('div'), then this function calls colli(). So now, as i have modified my function, i checked the error console and saw that it may take up to 5 tries for it to start working correctly. 5 x 2seconds, thats 10 seconds. It is never 5 retries always, may vary There's got to be something else going on?
In Firefox, childNodes can include #text nodes. You should check to make sure that childNodes[cEntry] has nodeType == 1 or has a getAttribute method before trying to call it. e.g.
<div id="d0">
</div>
<div id="d1"></div>
In the above in Firefox and similar browsers (i.e. based on Gecko and WebKit based browsers like Safari), d0 has one child node, a text node, and d1 has no child nodes.
So I would do something like:
var sCollNumber, el0, el1;
if (oPriorityMass) {
for (var cEntry=0; cEntry < oPriorityMass.childNodes.length; cEntry++) {
el0 = oPriorityMass.childNodes[cEntry];
// Make sure have an HTMLElement that will
// have a getAttribute method
if (el0.nodeType == 1) {
sCollNumber = el0.getAttribute('coll');
el1 = bynID('adder' + sCollNumber + '_check');
// Make sure el1 is not falsey before attempting to
// access properties
if (el1 && el1.checked)
// Never call parseInt on strings without a radix
// Or use some other method to convert to Number
aPriorities.push(parseInt(sCollNumber, 10));
}
}
Given that sCollNumber seems like it is a string integer (just guessing but it seems likely), you can also use:
Number(sCollNumber)
or
+sCollNumber
whichever suits and is more maintainable.
So, according to your last edit, it now works, with the delay, right?
But when I suggested the delay it was not meant to do (even more?) ajax calls while waiting!!
NOT:
if (!oPriorityMass.childNodes[0]) {
GM_log('Retrying');
setTimeout(loadPage,2000);
return;
More like:
setTimeout (colli, 2000);
So the ajax and the other stuff that loadPage does could explain the excessive delay.
The random behavior could be caused by:
return top.document.getElementById(ns(sID));
This will cause erratic behavior if any frames or iframes are present, and you do not block operation on frames. (If you do block such operation then top is redundant and unnecessary.)
GM does not operate correctly in such cases -- depending on what the script does -- often seeming to "switch" from top scope to frame scope or vice versa.
So, it's probably best to change that to:
return document.getElementById (ns (sID) );
And make sure you have:
if (window.top != window.self) //-- Don't run on frames or iframes
return;
as the top lines of code.
Beyond that, it's near impossible to see the problem, because of insufficient information.
Either boil the problem into a Complete, Self Contained, Recipe for duplicating the failure.
OR, post or link to the Complete, Unedited, Script.
I am trying to count the number of Tabs that are open in my google chrome browswer with javascript. Does anyone know how to do this?
I wrote some javascript that I want repeated 10 times and then stop. Upon the completion of 1 iteration, I open a new window using:
window.open("http://www.test.com");
I want to do this 10 times than stop. Maybe there is a better way than what I am thinking...
It's a good thing that webpages are sandboxed so that other websites can't access them. If they're windows that you've opened using window.open you can save the reference you receive to the window:
var win = window.open(url);
of course you could push this to an array if you're opening a large number of windows.
var wins = [];
//looping stuff here
wins.push(window.open(url[i]);
I think the loop is just fine, but if you want to keep track,
var winList = new Array();
var count = 10;
for(var i=0; i < count; i++){
winList[i] = window.open("http://www.test.com");
}
This way, you can keep references to your windows.
hth
So I couldn't figure out a way doing what I wanted so I took a different approach. I said, lets see if google has the option in chrome to limit the number of tabs opened and I found someone wrote an extension to do exactly that. I don't know how he did but it definitely works.
Controlled multi-tab browsing
Look at the Google Chrome Extensions Developer Guide , in particular the Tabs page and the getAllInWindow function
chrome.tabs.getAllInWindow(integer windowId, function callback)
Where the callback function receives an array of tabs. Meaning you can get its length.
And if the tabs you want to keep track of are possibly in different windows, then you need to look at the Windows page and the getAll function
chrome.windows.getAll(object getInfo, function callback)
Use this to iterate over all windows and call getAllInWindow. And you're all set.
If all you want to do is open ten tabs:
var i;
for (i = 0; i < 10; i++) {
window.open("http://www.test.com");
}
But no, I don't believe you can count the number of open tabs since that could disclose information to websites that you may not want them knowing. (Do you want random websites you visit to know how many tabs you have open?)
I have a list of check boxes. For the check boxes that are selected, I change it's name before submitting. In FF the function works. In IE I get:
A script on this page is causing Internet Explorer to run slowly. If it
continues to run, your computer may
become unresponsive.
Do you want to abort the script? YES/NO
Not sure why this loop is causing problems in IE and not FF?
function sub()
{
var x=document.getElementsByName("user");
for (i = 0; i < x.length; i++) //for all check boxes
{
if (x[i].checked == true)
{
x[i].name="id"; //change name of data so we know it is for an id
//By renaming the first element of the list, we have reduced the length of the list by one
//and deleted the first element. This is why we need to keep i at it's current position after a name change.
i=i-1;
}
}//end for
document.checks.submit();
}
I would avoid writing a script like that - it is like having an for/i++ loop calling a function that changes the index as a side effect - unpredictable. You run an iterator through NodeList while modifying the list from inside the loop. You cannot be sure it works until you happen to know exactly the way NodeList is implemented.
It's unpleasant, but I would first copy the list into "real" array, and then do the renaming.
This should work with a both a live and a non-live list.
Personally, though, I'd try to find some way to output the original page so that the server can figure out which elements to use, instead of relying on javascript to do it.
function sub()
{
var x=document.getElementsByName("user");
var nodesToChangeIndex=0;
var nodesToChange=new Array();
for (i = 0; i < x.length; i++) //for all check boxes
{
if (x[i].checked == true)
{
nodesToChange[nodesToChangeIndex++] = x[i];
}
}//end for
for(i=0; i < nodesToChangeIndex; i++)
{
nodesToChange[i].name="id";
}
document.checks.submit();
}
Internet Explorer is buggy. It doesn't return a live nodelist but just a snapshot.
Using a framework such as jQuery is your best bet in achieving full compatibility.
Edit: This is wrong, Nick is right. Although I'd look extra hard to make sure IE actually implements the NodeList correctly, since it still sounds like what you're running into is an infinite loop in IE.
Thanks for the heads up, Nick, I learned something new today. Javascript never ceases to surprise me :)
Just renaming an element in the array would not remove it from the array -- getElementsByName is not run constantly, just the initial time that it is called. So IE is stuck in an infinite loop where it keeps checking the same checked element over and over. I'm honestly not sure why Firefox doesn't also get stuck in the same infinite loop.
As far as I understand, the i=i-1 line is entirely unnecessary.